Answer:

Step-by-step explanation:
we know that
The density is equal to the mass divided by the volume
Let
x-----> the mass of marble
y----> the volume of marble
z----> the density of marble

in this problem we have


substitute and solve for x


He can count and there is 6.5 blocks between his house and the park
Answer:
b is the answer in your questions
5n-2=n+18
Move n to the other side
Sign changes from +n to -n
5n-n-2= n-n+18
5n-n-2= 18
4n-2= 18
Move -2 to the other side
Sign changes from -2 to +2
4n-2+2= 18+2
4n= 18+2
4n= 20
Divide by 4 for both sides
4n/4= 20/4
Answer: n=5